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A Discussion of the Water Content of Vermiculite

Published online by Cambridge University Press:  01 January 2024

W. F. Bradley  and
J. M. Serratosa
W. F. Bradley
Affiliation:
Illinois Geological Survey, Urbana, Illinois, USA
J. M. Serratosa
Affiliation:
Illinois Geological Survey, Urbana, Illinois, USA Institute de Edafologia, CSIC, Madrid, Spain
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Abstract

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Selected chemical and diffraction analyses from the literature, supplemented by thermal and thermogravimetric analyses and infrared absorption observations, are utilized to construct a rational model of the water arrangement in natural vermiculites.

A super cell is arranged by simple modification of the Hendricks water nets to accommodate the somewhat higher water contents, indicated by weight loss analyses, and the exchangeable cations.

A three-cell unit (15.6 × 9 Å) contains two Mg2+·6H2O octahedra centered at the corners and face centers and four 4H2O squares centered about ±5.2 Å along a between the octahedra. The arrangement affords twenty hydrogen bonds near 2.75 Å, twelve between silicate and water layers and eight between water layers, and thirty-two hydrogen bonds near 3.0 Å within water layers. The remaining four hydrogens are not active in the bonding system. The environment of each water molecule is a distorted tetrahedron.

A broad infrared absorption band shows maxima at about 3600, 3450 and 3350 cm−1 at normal incidence, with increased activity in the highest and lowest energies when a flake is tilted. It is concluded that OH axes in the shortest bonds are more inclined to the cleavage planes than are the intermediate length axes.

Type
Article
Information
Clays and Clay Minerals (National Conference on Clays and Clay Minerals) , Volume 7 , February 1958 , pp. 260 - 270
Copyright
Copyright © Clay Minerals Society 1958

References

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